This site has been a place of worship for 2 000 years: a Gallo-Roman temple, Christian basilica and Romanesque church all preceded the current building. Maurice de Sully began construction around 1163. Over the centuries it has suffered significant architectural maltreatment, remedied by the restoration work of Viollet-le-Duc and Lassus begun in 1841. It was one of the last great churches with galleries and one of the first to display flying buttresses; the addition of gargoyles to displace rainwater was another new innovation. From the top of the south tower, the view extends across Île de la Cité, upon which it is built.